Roles for Kisspeptin in proliferation and differentiation of spermatogonial cells isolated from mice offspring when the cells are cocultured with somatic cells

The interplay between kisspeptin and endocannabinoid systems modulates male hypothalamic and gonadic control of reproduction in vivo

Introduction

Male reproduction is under the control of the hypothalamus-pituitary-gonadal (HPG) axis. The endocannabinoid system (ECS) and the kisspeptin system (KS) are two major signaling systems in the central and peripheral control of reproduction, but their possible interaction has been poorly investigated in mammals. This manuscript analyzes their possible reciprocal modulation in the control of the HPG axis.

Materials and methods

Adolescent male rats were treated with kisspeptin-10 (Kp10) and endocannabinoid anandamide (AEA), the latter alone or in combination with the type 1 cannabinoid receptor (CB1) antagonist rimonabant (SR141716A). The hypothalamic KS system and GnRH expression, circulating sex steroids and kisspeptin (Kiss1) levels, and intratesticular KS and ECS were evaluated by immunohistochemical and molecular methods. Non-coding RNAs (i.e., miR145-5p, miR-132-3p, let7a-5p, let7b-5p) were also considered.

Results

Circulating hormonal values were not significantly affected by Kp10 or AEA; in the hypothalamus, Kp10 significantly increased GnRH mRNA and aromatase Cyp19, Kiss1, and Kiss1 receptor (Kiss1R) proteins. By contrast, AEA treatment affected the hypothalamic KS at the protein levels, with opposite effects on the ligand and receptor, and SR141716A was capable of attenuating the AEA effects. Among the considered non-coding RNA, only the expression of miR145-5p was positively affected by AEA but not by Kp10 treatment. Localization of Kiss1+/Kiss1R+ neurons in the arcuate nucleus revealed an increase of Kiss1R-expressing neurons in Kp10- and AEA-treated animals associated with enlargement of the lateral ventricles in Kp10-treated animals. In the brain and testis, the selected non-coding RNA was differently modulated by Kp10 or AEA. Lastly, in the testis, AEA treatment affected the KS at the protein levels, whereas Kp10 affected the intragonadal levels of CB1 and FAAH, the main modulator of the AEA tone. Changes in pubertal transition-related miRNAs and the intratesticular distribution of Kiss1, Kiss1R, CB1, and CB2 following KP and AEA treatment corroborate the KS-ECS crosstalk also showing that the CB1 receptor is involved in this interplay.

Conclusion

For the first time in mammals, we report the modulation of the KS in both the hypothalamus and testis by AEA and revealed the KP-dependent modulation of CB1 and FAAH in the testis. KP involvement in the progression of spermatogenesis is also suggested.

The Kisspeptin System in Male Reproduction

The kisspeptin system includes the cleavage products Kiss1 precursor and kisspeptin receptor (Kiss1R). It was originally discovered and studied in cancer metastasis, but the identification of KISS1/KISS1R gene mutations causing hypogonadotropic hypogonadism (HH) revealed unexpected effects in reproduction. Nowadays, the kisspeptin system is the main central gatekeeper of the reproductive axis at puberty and adulthood, but it also has a widespread functional role in the control of endocrine functions. At the periphery, Kiss1 and Kiss1R are expressed in the testes, but the need for kisspeptin signaling for spermatogenesis and sperm quality is still unclear and debated. This brief manuscript summarizes the main findings on kisspeptin and male reproduction; upcoming data on sperm maturation are also discussed.

Differential Expression of Kisspeptin System and Kisspeptin Receptor Trafficking during Spermatozoa Transit in the Epididymis

The hypothalamus–pituitary–testis axis controls the production of spermatozoa, and the kisspeptin system, comprising Kiss1 and Kiss1 receptor (Kiss1R), is the main central gatekeeper. The activity of the kisspeptin system also occurs in testis and spermatozoa, but currently the need of peripheral kisspeptin to produce gametes is not fully understood. Hence, we characterized kisspeptin system in rat spermatozoa and epididymis caput and cauda and analyzed the possible presence of Kiss1 in the epididymal fluid. The presence of Kiss1 and Kiss1R in spermatozoa collected from epididymis caput and cauda was evaluated by Western blot; significant high Kiss1 levels in the caput (p < 0.001 vs. cauda) and constant levels of Kiss1R proteins were observed. Immunofluorescence analysis revealed that the localization of Kiss1R in sperm head shifts from the posterior region in the epididymis caput to perforatorium in the epididymis cauda. In spermatozoa-free epididymis, Western blot revealed higher expression of Kiss1 and Kiss1R in caput (p < 0.05 vs. cauda). Moreover, immunohistochemistry revealed that Kiss1 and Kiss1R proteins were mainly localized in the secretory epithelial cell types and in contractile myoid cells, respectively. Finally, both dot blot and Elisa revealed the presence of Kiss1 in the epididymal fluid collected from epididymis cauda and caput, indicating that rat epididymis and spermatozoa possess a complete kisspeptin system. In conclusion, we reported for the first time in rodents Kiss1R trafficking in spermatozoa during the epididymis transit and Kiss1 measure in the epididymal fluid, thus suggesting a possible role for the system in spermatozoa maturation and storage within the epididymis.

Cryoprotective Effect of Pentoxifylline on Spermatogonial Stem Cell During Transplantation into Azoospermic Torsion Mouse Model

Preserving the spermatogonial stem cells (SSCs) in long periods of time during the treatment of male infertility using stem cell banking systems and transplantation is an important issue. Therefore, this study was conducted to develop an optimal cryopreservation protocol for SSCs using 10 mM pentoxifylline (PTX) as an antioxidant in basal freezing medium. Testicular torsion-a mouse model for long-term infertility-was used to transplant fresh SSCs (n = 6), fresh SSCs treated with PTX (n = 6), cryopreserved SSCs with basal freezing medium (n = 6), and cryopreserved SSCs treated with PTX (n = 6). Eight weeks after germ cell transplantation, samples were assessed for proliferation, through evaluation of Ddx4 and Id4 markers, and differentiation via evaluation of C-Kit and Sycp3, Tnp1, Tnp2, and Prm1 markers. According to morphological and flow cytometry results, SSCs are able to form colonies and express Gfra1, Id4, α6-integrin, and β1-integrin markers. We found positive influence from PTX on proliferative and differentiative markers in SSCs transplanted to azoospermic mice. In the recipient testis, donor SSCs formed spermatogenic colonies and sperm. Respecting these data, adding pentoxifylline is a practical way to precisely cryopreserve germ cells enriched for SSCs in cryopreservation, and this procedure could become an efficient method to restore fertility in a clinical setup. However, more studies are needed to ensure its safety in the long term.

Kiss1 is differentially regulated in male and female mice by the homeodomain transcription factor VAX1

Regulation of Kiss1 transcription is crucial to the development and function of the reproductive axis. The homeodomain transcription factor, ventral anterior homeobox 1 (VAX1), has been implicated as a potential regulator of Kiss1 transcription. However, it is unknown whether VAX1 directly mediates transcription within kisspeptin neurons or works indirectly by acting upstream of kisspeptin neuron populations. This study tested the hypothesis that VAX1 within kisspeptin neurons regulates Kiss1 gene expression. We found that VAX1 acts as a repressor of Kiss1 in vitro and within the male arcuate nucleus in vivo. In female mice, we found that the loss of VAX1 caused a reduction in Kiss1 expression and Kiss1-containing neurons in the anteroventral periventricular nucleus at the time of the preovulatory luteinizing hormone surge, but was compensated by an increase in Kiss1-cFos colocalization. Despite changes in Kiss1 transcription, gonadotropin levels were unaffected and there were no impairments to fertility.

The guardians of germ cells; Sertoli-derived exosomes against electromagnetic field-induced oxidative stress in mouse spermatogonial stem cells

Nowadays, prolonged exposure to electromagnetic fields (EMF) has raised public concern about the detrimental potential of EMF on spermatogonial stem cells (SSCs) and spermatogenesis. Recent studies introduced the fundamental role of Sertoli cell paracrine signaling in the regulation of SSCs maintenance and differentiation in fertility preservation. Thus we investigated the therapeutic effect of Sertoli-derived exosomes (Sertoli-EXOs) as powerful paracrine mediators in SSCs subjected to EMF and its underlying mechanisms. SSCs and Sertoli cells were isolated from neonate mice testis, and identified by their specific markers. Then SSCs were exposed to 50 Hz EMF with intensity of 2.5 mT (1 h for 5 days) and supplemented with exosomes that were isolated from pre-pubertal Sertoli cells. Sertoli-EXOs were characterized and the uptake was observed by PKH26 labeling. The cell viability, colonization efficiency, reactive oxygen species (ROS) balance, cell cycle arrest and apoptosis induction were then analysed. SSCs were confirmed by immunocytochemistry (Oct4, Plzf) and Sertoli cells were identified through Sox9 and vimentin expression by immunocytochemistry and Real-time PCR (qRT-PCR), respectively. Our results demonstrated the detrimental effect of EMF via ROS accumulation that reduced the expression of catalase antioxidant, cell viability and colonization of SSCs. Also, AO/PI and flow cytometry analysis demonstrated the elevation of apoptosis in SSCs exposed to EMF in comparison with control. qRT-PCR data confirmed the up-regulation of apoptotic gene (Caspase-3) and down-regulation of SSCs specific gene (GFRα1). Consequently, the administration of Sertoli-EXOs exerted ameliorative effect on SSCs and significantly improved these changes through the regulation of oxidative stress. These findings suggest that Sertoli-EXOs have positive impact on SSCs exposed to EMF and can be useful in further investigation of Sertoli-EXOs as a novel therapeutic agent which may recover the deregulated SSCs microenvironment and spermatogenesis after exposure to EMF.

POSTN Promotes the Proliferation of Spermatogonial Cells by Activating the Wnt/β-Catenin Signaling Pathway

The self-renewal of spermatogonial cells (SCs) provides the foundation for life-long spermatogenesis. To date, only a few growth factors have been used for the culture of SCs in vitro, and how to enhance proliferation capacity of SCs in vitro needs further research. This study aimed to explore the effects of periostin (POSTN) on the proliferation of human SCs. GC-1 spg cells were cultured in a medium with POSTN, cell proliferation was evaluated by MTS analysis and EdU assay, and the Wnt/β-catenin signaling pathway was examined. Thereafter, the proliferations of human SC were detected using immunofluorescence and RT-PCR. In this study, we found that CM secreted by human amniotic mesenchymal stem cells (hAMSCs) could enhance the proliferation capacity of mouse GC-1 spg cells. Label-free mass spectrometry and ELISA analysis demonstrated that high level of POSTN was secreted by hAMSCs. MTS and EdU staining showed that POSTN increased GC-1 spg cell proliferation, whereas CM from POSTN-silenced hAMSCs suppressed cell proliferation capacity. Then POSTN was found to activate the Wnt/β-catenin signaling pathway to regulate the proliferation of GC-1 spg cells. XAV-939, a Wnt/β-catenin inhibitor, partially reversed the effects of POSTN on GC-1 spg cell proliferation. We then analyzed human SCs and found that POSTN promoted human SC proliferation in vitro. These findings provide insights regarding the role of POSTN in regulating SC proliferation via the Wnt/β-catenin signaling pathway and suggest that POSTN may serve as a cytokine for male infertility therapy.

Pentoxifylline improves the survival of spermatogenic cells via oxidative stress suppression and upregulation of PI3K/AKT pathway in mouse model of testicular torsion-detorsion

Testicular torsion-detorsion results in enhanced formation of free radicals which contribute to the pathophysiology of testicular tissue damage. Recent reports have identified protective role of pentoxifylline (PTX) against free radicals. Thus, we determined the protective effect of pentoxifylline against testicular damage in mouse model of testicular torsion-detorsion.

Twenty (6 weeks old) male mice were divided into 4 groups of 5 animals each namely: Control (sham operated group), T1 (Torsion-detosion + single dose 100 mg/kg PTX, T2 (torsion-detorsion + 20 mg/kg PTX for 2 weeks and T/D (torsion-detorsion only). Animals in T1, T2 and T/D groups underwent 2 h of testicular torsion with the left testes rotated 720° (clockwisely) followed by 30 min of detorsion. After detorsion, drug administration was done intraperitoneally. The left testes of all the animals were excised on the 35th day after torsion-detortion for histopathological and biochemical assay. Histomorphological analysis of the seminiferous tubules showed that there were significant increase (P < 0.01 or 0.05) in the mean seminiferous tubule diameter, Johnson score and germ cells of animals in Control and T1 compared to T2 and T/D with no significant difference (P > 0.05) in testes weight, sertoli, leydig and myoid cells in all groups. IHC results showed significant increase (P < 0.01 or 0.05) in id4 and scp3 protein markers in Control, T1 and T2 compared to T/D. Oxidative stress analysis revealed that Pentoxifylline significantly increased (P < 0.01 or 0.05) the level of SOD, catalase, mRNA expression of akt and pi3k genes but significantly suppress (P < 0.01 or 0.05) MDA and Caspase-3 level in Control, T1 and T2 compared to T/D. Pentoxifylline could be used as an adjunct therapy to surgery in the treatment of torsion-detorsion related testicular injury, However, Further studies are needed to evaluate the effects of pentoxifylline on testicular torsion.

Effect of a Freezing Medium Containing Melatonin on Markers of Pre-meiotic and Post-meiotic Spermatogonial Stem Cells (SSCs) After Transplantation in an Azoospermia Mouse Model Due to Testicular Torsion

Spermatogonial stem cells (SSCs) are essential to the initiation of spermatogenesis. Cryopreservation, long-term maintenance, and auto-transplantation of SSCs could be a new treatment for infertility. The aim of this study was to add melatonin to the basic freezing medium and to evaluate its effect on the efficiency of the thawed SSCs after transplantation into the testicles of azoospermic mice. SSCs were isolated from newborn NMRI mice, and the cells were enriched to assess morphological features. The thawed SSCs were evaluated for survival, apoptosis, and ROS level before transplantation, and the proliferation (MVH and ID4) and differentiation (c-Kit, SCP3, TP1, TP2, and Prm1) markers of SSCs were examined using immunofluorescence, western blot, and quantitative real-time polymerase chain reaction (PCR) after transplantation. It was found that the survival rate of SSCs after thawing was significantly higher in the melatonin group compared with the cryopreservation group containing basic freezing medium, and the rate of apoptosis and level of ROS production also decreased significantly in the cryopreservation group with melatonin (p < 0.05). The expression of proliferation and differentiation markers after transplantation was significantly higher in the cryopreservation group with melatonin compared to the cryopreservation group (p < 0.05). The results suggest that adding melatonin to the basic freezing medium can effectively protect the SSCs by increasing the viability and reducing the ROS production and apoptosis and improve the transplantation efficiency of SSCs after cryopreservation, which will provide a significant suggestion for fertility protection in the clinic.

Kisspeptins, new local modulators of male reproduction: A comparative overview

Spermatogenesis is a complex process that leads to the production of male gametes within the testis through the coordination of mitotic, meiotic and differentiation events, under a deep control of endocrine, paracrine and autocrine modulators along the Hypothalamus-pituitary-gonad (HPG) axis. The kisspeptin system plays a fundamental role along the HPG axis as it is the main positive modulator upstream of the hypothalamic neurons that secrete the Gonadotropin Releasing Hormone (GnRH), the decapeptide that supports pituitary gonadotropins and the production of gonadal sex steroid. Currently, kisspeptins and their receptor, KISS1R, have a recognized activity in the central control of puberty onset, sex maturation, reproduction and sex-steroid feedback mechanisms in both animal models and human. However, kisspeptin signaling has been widely reported in peripheral tissues, particularly in the testis of mammalian and non-mammalian vertebrates, with functions related to Leydig cells physiology and steroid biosynthesis, spermatogenesis progression and spermatozoa functions, but its mandatory role within the testis is still a matter of discussion. This review provides a summary of the main intratesticular effects of kisspeptin in vertebrates, via a comparative approach. Particular emphasis was devoted to data from the anuran amphibian Pelophylax esculentus, the first animal model in which the direct intratesticular activity of kisspeptin was reported.

Kisspeptin and Testicular Function-Is it Necessary?

The role of kisspeptin in stimulating hypothalamic GnRH is undisputed. However, the role of kisspeptin signaling in testicular function is less clear. The testes are essential for male reproduction through their functions of spermatogenesis and steroidogenesis. Our review focused on the current literature investigating the distribution, regulation and effects of kisspeptin and its receptor (KISS1/KISS1R) within the testes of species studied to date. There is substantial evidence of localised KISS1/KISS1R expression and peptide distribution in the testes. However, variability is observed in the testicular cell types expressing KISS1/KISS1R. Evidence is presented for modulation of steroidogenesis and sperm function by kisspeptin signaling. However, the physiological importance of such effects, and whether these are paracrine or endocrine manifestations, remain unclear.

Reproductive, antioxidant and metabolic responses of Ossimi rams to kisspeptin

The aim of this study was to evaluate the potential reproductive, antioxidant and metabolic effects of kisspeptin-10 (KP-10) on Ossimi rams. Twelve Ossimi rams (1.5-2 years old) were divided randomly into two groups (six per group). The first one served as a control group, while the second one served as a treated group. Rams of the treated group were injected once weekly with KP-10 (5 μg/kg body weight) for one month. There were no significant differences in all measured parameters between rams of control group at pre-treatment period and those at post-treatment period. However, most examined parameters in the same rams in the treated group were affected by injection of KP-10 when comparing pre-treatment values in treated group with its post-treatment values. At the pre-treatment period, there were no significant differences between the treated and control groups regarding semen pH, mass motility, sperm concentration/mL, live and dead spermatozoa, total sperm abnormality, testosterone and oxidative stress and metabolic parameters. However, all semen characteristics were significantly improved in the treated group compared with the control group at the post-treatment period and in the treated group at the post-treatment period compared with that at the pre-treatment period. In addition, scrotal circumference, ejaculate volume and total sperm concentration/ejaculate showed higher significant improvements when comparing the treated group with the control one at the post-treatment period than when comparing the two groups at the pre-treatment period and also when comparing the treated group at the post-treatment period with that at the pre-treatment period. Serum testosterone, total antioxidant capacity, lipid peroxides, nitric oxide, total protein, albumin, glucose and high density lipoprotein-cholesterol levels significantly increased when comparing the treated group with the control one at the post-treatment period and also when comparing the treated group at the post-treatment period with that at the pre-treatment period. In conclusion, KP-10 led to potential improvement in the reproductive efficacy and metabolic capacity of Ossimi ram.